Supplementary firing system



ly 29, 1969 E. G. GJERDE 3,457,902

SUPPLEMENTARY FIRING SYSTEM Original Filed March 5, 1967 2 Sheets-Sheetl a H H {+2 .7 F Go I 1 I Q 50/452 f T? pom/2 q as ourPar TUZEl/VE N Z FG 5 27 FUEL 44s 64 VD 1 A 97 66 a? l INVENTOR. [QW/N I 475225 Ar 702m:KS

United States Patent Int. Cl. F22d 1/00 U.S. Cl. 122-7 16 ClaimsABSTRACT OF THE DISCLOSURE A firing system for heating the exhaust froma gas turbine to an elevated temperature and injecting the heatedexhaust into heat exchange relationship with a boiler for heating theboiler. The system includes a duct interconnecting the exhaust port ofthe turbine and the heat receiving compartment of the boiler and aframe, which has a central passage that complements the crosssectionalflow area of the duct, is supported in the wall of the duct. A pluralityof elongated gas conduits are arranged in spaced relationship within thepassage and are supported from the frame. Each of the conduits includesa series of orifices that open toward the boiler. A plurality of burnerheads, corresponding in number to the number of conduits, are supportedfrom the respective conduits and each includes a pair of opposed sidewalls which cooperate to form aligned inlet and outlet openings, therespective inlets confronting the orifices of the respective conduitsand being co-extensive therewith. The walls extend away from the inletand angle inwardly toward each other to form a throat and then turnoutwardly in opposite directions to form a shelf and then turn towardthe boiler and extend parallel of one another to form opposite sides ofa combustion chamber and finally terminate in edges which cooperate todefine the outlet opening. The burners being adapted to receive at least40% but not more than 75% of the exhaust flowing through the passage.

This is a continuation of application Serial No. 620,459, filed Mar. 3,1967, now abandoned.

BACKGROUND OF INVENTION Field of invention.The present invention relatesgenerally to systems for utilizing heat from the exhaust of a gasturbine and more particularly to a system that includes a heater foradding heat to the exhaust and which utilizes the heated exhaust to heata boiler.

Description of prior art.Existing systems for heating the exhaustemitted from gas turbines include a plurality, generally six or seven,of relatively large burners or heater heads that are disposed in theduct leading from the turbine to the boiler. Heaters of this type do notprovide optimum results since the turbine exhaust flowing by the heatersis not sufiiciently exposed to and mixed with the flame being emittedfrom the heaters. Since the heads are relatively large the flamesemitted therefrom are relatively long and the projecting tips are at arelatively low temperature thus effecting ineflicient burning of thefuel.

SUMMARY OF INVENTION A particular object of the present invention is toprovide a supplementary heating system that includes a gas turbine, aboiler and a duct interconnecting the exhaust port of the turbine withthe heat receiving compartment of the boiler. A frame is supported inthe wall of the duct and includes a central passage having aconfiguration that complements the internal cross-sectional flow area ofthe duct. A plurality of gas conduits having a series of orifices spacedalong their lengths are arranged in spaced relationship throughout thepassage and are supported from 3,457,902 Patented July 29, 1969 theframe with the orifices directed toward the boiler. A plurality ofelongated burner heads, corresponding in number to the number ofconduits, are each supported from the respective conduits and include apair of opposed walls which cooperate to form aligned inlet and outletopenings, the respective inlets being spaced from the respectiveconduits and confronting the respective orifices formed by suchconduits. The burner heads are sized to cumulatively receive at least40% but not more than of the exhaust flow through said passage. Thewalls extend away from the inlets and angle inwardly toward each otherto form a throat and then turn outwardly in opposite directions to forma shelf and then turn and extend parallel of each other and toward theboiler to form opposite walls of a combustion chamber and finallyterminate in edges which cooperate to form the outlet.

Other objects and advantages of the present invention will becomeapparent from the following detailed description of a preferredembodiment thereof, when taken in conjunction with the appendeddrawings.

DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view of a systemembodying the present invention;

FIG. 2 is an elevational sectional view taken along the lines 22 of FIG.1;

FIG. 3 is a partial view, in enlarged scale, taken from thebroken-circle designated 3 in FIG. 2;

FIG. 4 is an elevational sectional view taken along the lines 4-4 ofFIG. 3;

FIG. 5 is a broken horizontal sectional view, in enlarged scale, takenalong the lines 5-5 of FIG. 2;

FIG. 6 is a broken horizontal sectional view, in enlarged scale, takenalong the lines 6-6 of FIG. 2;

FIG. 7 is an elevational sectional view, in enlarged scale, taken alongthe lines 77 of FIG. 6; and

FIG. 8 is a partial exploded view, in enlarged scale, taken along thelines 88 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 it is commonpractice in industry to provide a gas turbine T for driving a generatorG which in turn drives a work load L. The exhaust from the turbine Tcontains a substantial amount of heat but it is not at a high enoughtemperature to be utilized to heat a conventional boiler B. According tothe present invention, the turbine T exhaust port is connected with theheat receiving compartment of the boiler B by a duct D which has anenlarged section in which is installed a heater H.

Referring to FIG. 2, the heater H broadly includes a frame 13 that formsa central passage 15 for passage of the turbine exhaust. A plurality ofhorizontally extending gas conduits 17 are spaced equidistantly from oneanother and are supported in the passage 15 by housings 19. Each of theconduits 17 include a series of orifices 23 spaced along their lengthsand opening toward the boiler B. A plurality of elongated burner heads,generally designated 27, corresponding in number to the number ofconduits 17, are supported coextensive with and behind the respectiveconduits and include aligned inlet and outlet openings 29 and 31,respectively, the respective inlets facing upstream of the exhaust andconfronting the orifices 23 for receiving flow as indicated by thedirectional arrows in FIG. 4. A flow restricting throat 33 is formedintermediate the openings 29 and 31 and a combustion chamber 37 isformed immediately downstream thereof and is open on its downstream endto form the outlet opening 31.

More particularly the frame 13 includes four outer flanged steel beams41 and conventional thermal lining 43 which is sandwiched between thebeams 41 and refractory 45. The housings 19 are tubular in shape and aresup.- ported at their ends in aligned horizontal bores 51 and 52 formedin the refractory 47 and thermal liner 43, the bores 52 on the left-handends, FIG. 2, being fitted with pipes 54 which freely receive thehousings 19 and allow axial movement to provide for axial thermalexpansion. The tubular housings 19 form passages 53 for receiving theconduits 17 and have a series of flared apertures 57 that confront therespective orifices 23 for passage of the gas jet emitted therefrom.

Referring to FIGS. 4 and 5, the burner heads 27 are conveniently made insections 58 and each section includes a pair of opposed end walls 56,for securing such sections to the respective housings 19, as by nut andbolt assemblies 61 which span the housings and receive curved clips 62.A pair of opposed walls 59 and 60 cooperate to form the inlet and outletopenings 29 and 31, respectively, angle inwardly toward each other fromthe inlet to form the throat 33, and then flare outwardly to formshelves 63. The walls 59 and 60 turn downstream from the shelves 63 andextend parallel of one another to form the chamber 37 and are turnedinwardly at their extremities to form confronting lips 64, the edges ofthe lips cooperating to define the opening 31. Vortex bars 65 aresupported from the walls 59 and 60 and confront the respective orifices23 to interrupt the gas jet emitted therefrom and induce mixing of theunaerated gas with the aerated entering exhaust. Since the gas suppliedto the conduits 17 is generally unaerated the inlet 29 is sized toassure that suflicient oxygen containing exhaust is received thereby toprovide an optimum ratio of oxygen to gas in the chamber 37 duringsteady state operation of the system.

A particular advantage of the heater H is that the gas conduits 17 canbe removed from the housings 19 for cleaning without interruptingoperation of the heater. To this end each conduit 17 extends through ahousing valve 66 and is communicative with a heater manifold 67extending along one side of the frame 13. A plurality of bores 69,corresponding to the number of conduits 17, are spaced along the wall ofthe manifold 67 and a nipple 79 is welded into each. Conventional ballvalves 81 are attached on one end to the respective nipples 79 andreceive a nipple 83 on their opposite ends. A union 85 is screwed ontoeach of the nipples 83 and receives another nipple 87 onto which isscrewed a T 89. The vertical flange of the right-hand beam 41, as viewedin FIG. 2, includes a series of horizontal bores 93 for projection ofthe conduits 17. Referring to FIG. 6, flanges 97 are welded to the webof such I-beam 41 and include central bores into which are weldednipples 99. The housing valves 66 are screwed onto the nipples 99 andhollow index fittings 107 are screwed into their extending ends. Thefittings 107 include outwardly facing annular index surfaces 111 withintheir passage, such surfaces being abutted by indexing surfaces 115formed by the inner end of index rings 117 welded to the conduits 17.Referring to FIG. 7, the rings 117 include longitudinal grooves 121 forreceiving a cooperating key 123 formed by the fittings 107. With thisarrangement, the conduits 17 are indexed longitudinally and radiallywithin the housings 19 such that the orifices 23 are aligned with theapertures 57. Annular plugs 129 slide over the extending conduits 17 andthread into the fittings 107 and press packing washers 131 against therings 117. The projecting ends of the conduits 17 are threaded forreceiving unions 135 which receive nipples 137 that are threaded intothe Ts 89. The unconnected end of the Ts 89 are plugged by plugs 141 andthe remote end of the conduits 17 are closed off by similar plugs 142.

A vertically extending starter, generally designated 149, is centrallylocated in the passage and is disposed behind the above describedhousings 19 and supported therefrom. The starter 149 is constructedsimilarly to the above described conduits 17 and burner heads 27, exceptthat it extends vertically rather than horizontally. Referring to FIG.8, the housings 19 of the starter 149 is clamped to each of thehorizontal housings 19 by means of clamps generally designated 153.These clamps 153 include a pair of oppositely facing rockers 157 thatare welded together on their crossing back sides and which areinterposed between the crossing housings 19. A saddle 159 includes fourstuds 161 projecting from its corners for over-fitting the crossingdefined by the intersection of the housings 19. A pair of pipe brackets163 each include a pair of bores 165 for receiving the studs 161 and aresecured in place by nuts 167 which thread onto the studs 161.

A conventional pilot light 171, having an ignition electrode (not shown)in electrical circuitry with an electrical actuating circuit, is mountedat the bottom end of the starter 149 and receives gas from an auxiliarygas line (not shown).

A conventional flame rod is bent over the housing of the pilot light 171and cooperates with electric circuitry (not shown) to open a solenoidvalve (not shown) that controls flow to the starter 149. A flame rod177, similar to rod 175, is bent over the upper end of the starter 149and cooperates with electrical circuitry (not shown) to open a solenoidvalve (not shown) which controls gas flow to the manifold 67. Thepurpose of the rods 175 and 177 will be described hereinafter.

From the foregoing it will be apparent that when the turbine T isoperated the exhaust emitted therefrom and into the duct D will be at anelevated temperature, as for instance 800 degrees F., and that when thisexhaust is passed through the heater H it will be heated to an evenhigher temperature, as for instance 1300 degrees F., and that thisrelatively high temperature mass of exhaust will be extremely effectivein heating the boiler B. Since the turbine exhaust is generallytravelling at a relatively high velocity, as for instance 3550 feet perminute, it is desirable to slow a portion thereof down and create arelatively low pressure combustion area where combustion will be assuredat all times irrespective of erratic velocity increases which may tendto blow-out the flame. Referring to FIGS. 2 and 4, it will be clear thata substantial portion depending on the size of the inlets 29 and numberof heads 27, of the turbine exhaust which passes through the passage 15will be received by the inlets 29 and will be passed through the heads27. In order to obtain optimum heating of the exhaust and provide aneven temperature profile across the crosssectional area of the duct Dwithin a short distance downstream of the heads 27, it has beendetermined that the combined area of the inlets 29 should comprisebetween 40 and 75% of the entire area of the passage 15. Restriction ofthe rapidly flowing exhaust in the throat 33 and expansion in thecombustion chamber 27 creates a venturi action to effect a pressure dropin the combustion chamber and such pressure drop is enhanced by the lips64. The gas jet emitted from the orifices 23 is impinged on the vortexbars 65 to create turbulence in the chamber 37, thereby effecting mixingand aeration of the gas. When the pilot light 171 is actuated the flamerod 175 will be engulfed in flame and will generate a small amount ofelectric current which will effect opening of the valve (not shown)associated with the starter 149 and the flame will be propagatedvertically across the center of the horizontal burner heads 27. When theflame reaches the top end of the starter 149 the flame rod 177 will beengulfed in flame and will be heated to generate electric current toopen the valve (not shown) associated with the manifold 67 and thehorizontal heads 27 will be ignited. The above described low pressure ofthe thoroughly mixed gas and exhaust in the chambers 37 will createoptimum conditions for rapid combustion thus resulting in a relativelyhigh temperature in the chambers. Such high temperature coupled withsufficient aeration of the gas will induce complete combustion of thegas within a short distance downstream of the high temperature chamber37 and will enhance burning efficiency. As the heated mixture flows fromthe openings 31 it will be immediately exposed to the surroundingexhaust and the turbulence resulting from flow by and through the heads27 will cause complete mixing with such exhaust thereby providing auniform temperature profile across the cross-section of flow.

In industrial applications, it is common practice to recover used gasfrom various processes and utilize it as fuel for heaters such as heaterH. Such gas generally has a relatively high level of contaminantssuspended therein and when it is exposed to oxygen at comparatively hightemperatures the contaminants oxidize immediately and will adhere tosurrounding surfaces. Thus, when the gas is emitted from the orifice 23oxidation takes place and slag will build-up around the walls of theorifices tending to plug them. Accordingly it is necessary to remove theconduits periodically and clean the orifice 23. A particular advantageof the present invention is that the individual conduits 17 can beremoved without necessity of discontinuing operation of the heaterH..This is accomplished by turning off the gas valve 81 associated withthe particular conduit 17 to be removed and disconnecting the unions 85and 135. The annular plug 129 is then removed to free the conduit 17 andsuch conduit is pulled from the housing 19. The valve 66 is then closedto prevent flame and hot exhaust which entered the orifices of thehousings 19 from being blown out the open end of the fitting 107. Thusthe removed conduit 17 can be cleaned and readied for reinstallationWithout discontinuing operation of the heater H.

From the above it will be apparent that the supplementary firing systemof this invention is inexpensive to manufacture and operate and that theheater H provides for proper fuel to air mixture and complete combustionof the fuel at relatively high temperature. The heater also inducesthorough mixing of the heated exhaust with the unheated exhaust toassure uniform heat impingement on the boiler B.

Various modifications and changes may be made with regard to theforegoing detailed description without departing from the spirit of theinvention or the scope of the following claims.

I claim:

1. A supplementary firing system comprising:

a gas turbine;

a boiler;

a duct interconnecting the exhaust port of said turbine and the heatreceiving compartment of said boiler;

a frame disposed in the wall of said duct and having a through centralpassage that complements the crosssectional flow area of said duct;

a plurality of elongated gas conduits supported from said frame andarranged in spaced relationship throughout said passage and eachincluding a series of orifices spaced along its length and directedtoward said boiler;

a plurality of elongated burner heads, corresponding in number to thenumber of said conduits are supported from said conduits and eachincludes .a pair of opposed side walls coextensive with said respectiveconduits and cooperating With one another to form aligned inlet andoutlet openings, said respective inlet openings confronting saidorifices included in said respective conduits, said pair of wallsfurther extending away from said inlet opening and angling inwardlytoward one another to form a throat, then turning outwardly from oneanother to form a shelf, then turning toward said boiler and extendingparallel of one another to form opposite walls of a combustion chamberand finally terminating the edges which cooperate to define said outletopena;

said burner heads being adapted to receive at least 40% but not morethan 75% of said exhaust flowing through said passage.

2. A firing system as set forth in claim 1 wherein said burner headsinclude a plurality of vortex bars, corresponding in number to thenumber of orifices in said respective conduits, said bars confrontingsaid respective orifices and being supported from said pair of sidewalls.

3. A firing system as set forth in claim 1 wherein said gas conduitsextend parallel of one another.

4. A firing system as set forth in claim 3 that includes a starter, saidstarter including an elongated gas conduit extending transversely of andadjacent to said plurality of conduits and including a plurality oforifices spaced along its length;

a burner head supported from said conduit and including a pair ofopposed side walls coextensive with said conduit and cooperating withone another to form aligned inlet and outlet openings, said inletopening confronting said orifices, said pair of side walls furtherextending away from said inlet opening and angling inwardly toward oneanother to form a throat, then turning outwardly from one another toform a shelf, then turning toward said boiler and extending parallel ofone another to form opposite walls of a combustion chamber and finallyterminating in edges which cooperate to define said outlet opening.

5. A heater as set forth in claim 4 wherein said starter is disposedintermediate the ends of said plurality of conduits.

6. A heater as set forth in claim 4 that includes a flame rod having itsextending portion adjacent one of said starter Walls forming said outletwhereby the latter acts as an electric ground relative thereto.

7. A heater as set forth in claim 4 that includes a pilot at one end ofsaid starter.

8. A heater as set forth in claim 7 that includes a flame rod having itsextending portion adjacent said pilot whereby the latter acts as anelectric ground relative thereto.

9. A supplementary firing system, comprising:

a gas turbine;

heat-transfer means;

a duct interconnecting the exhaust port of said turbine and theheat-receiving compartment of said heattransfer means;

conduit support means disposed in the wall of said duct;

a plurality of elongated gas conduits supported from said conduitsupport means and arranged in spaced relationship throughout saidpassage, each of said gas conduits including a series of orifices spacedalong its length and directed towards said heat-transfer means;

a plurality of elongated burner heads, corresponding in number to thenumber of said conduits supported from said conduits and each includinga pair of opposed side walls coextensive with said respective conduitsand cooperating with one another to form aligned inlet and outletopenings, said respective inlet openings confronting said orificesincluded in said respective conduits, said pair of walls furtherextending away from said inlet opening and angling inwardly towards oneanother to form a throat, then turning outwardly from one another toform opposite walls of a combustion chamber having said outlet opening;and

a vortex bar supported from each of said pair of side walls andconfronting said orifices to interrupt the gas jet emitted therefrom andinduce mixing and aeration of the gas with the entering exhaust, withsaid entering exhaust being restricted in said throat and expanded insaid combustion chamber to effect a pressure drop within said combustionchamber.

10. A firing system as set forth in claim 9 wherein said burner headsare adapted to receive at least 40% but not more than 75 of said exhaustflowing through said passage.

11. A firing system as set forth in claim 9 wherein said gas conduitsextend parallel of one another.

12. A firing system as set forth in claim 9 that includes a starter,said starter including an elongated gas conduit extending transverselyof and adjacent to said plurality of conduits .and including a pluralityof orifices spaced along its length;

a burner head supported from said conduit and including a pair ofopposed side walls coextensive with said conduit and cooperating withone another to form aligned inlet and outlet openings, said inletopening confronting said orifices, said pair of side walls furtherextending away from said inlet opening and angling inwardly, toward oneanother to form a throat, then turning outwardly from one another toform a shelf, then turning toward said boiler and extending parallel ofone another to form opposite Wall of a combustion chamber and finallyterminating in edges which cooperate to define said outlet opening.

13. A heater as set forth in claim 9 wherein said starter is disposedintermediate the ends of said plurality of conduits.

14. A heater as set forth in claim 9 that includes a flame rod havingits extending portion adjacent one of said starter walls forming saidoutlet whereby the latte acts as an electric ground relative thereto.

15. A heater as set forth in claim 9 that includes a pilot at one end ofsaid starter.

16. A heater as set forth in claim 9 that includes a flame rod havingits extending portion adjacent said pilot whereby the latter acts as anelectric ground relative thereto.

References Cited UNITED STATES PATENTS 2,926,493 3/ 1960 Poole et al.

CHARLES I. MYHRE, Primary Examiner

